Mail Connector fails to flow from O365 to Domino after a period of time (4348169)

• Coexistence Manager for Notes (CMN) server is set up as Azure VM
• VPN from Azure to on-premise
• Mail Connector fails to flow from O365 to Domino after a period of time
• Errors similar to the following are seen in the CMN log:

2013-11-05 14:43:43,763 WARN  CMN.logging [Proxy 106] - Message Number [106] on Thread [15] from Exchange (207.46.163.157:58504) to Domino (10.10.10.10:25): A communications failure or interuption was encountered. - IOException: Unable to read data from the transport connection: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond